1. Field of the Invention
This invention relates generally to portable power tools, and in particular to a manually operated internal combustion power handle assembly and to attachments thereto to produce line trimmers, lawn edgers, brush cutters, tillers, hedge trimmers, power hacksaws, chain saws, water pumps, generators, air compressors, blowers, vacuums and the like.
2. Description of the Prior Art
It is well known in the prior art to provide two-stroke internal combustion engines or electric motors for driving portable machinery such as chain saws, lawnmowers, flexible line trimmers and the like. Various attempts have been made to adapt internal combustion engines for portable power tools which have a rotary head such as a brush cutter or flexible line trimmer. In the typical prior art arrangement, the rotary head of the power tool is connected by means of a drive shaft enclosed within a long tubular housing and is connected in driving relation at the opposite end to the internal combustion engine. The engine is typically mounted in such a manner that the engine is laterally offset relative to the drive shaft or is supported behind the operator when in use. This makes the engine extremely awkward to start, and requires that the operator must either set the unit on the ground to start it, or try to reach back over his shoulder and start it, or maneuver it as best he can with both hands to start it. Furthermore, in those units in which the engine is mounted in the rear, and the operator's hands are placed forward of the engine, a separate throttle arrangement and handle must be installed with a control cable leading back to the engine to control the throttle valve. This has resulted in loose wires moving about and becoming entangled in brush resulting in damage to the assembly.
Attachments for chain saws have been proposed to provide flexible line trimmers, etc. However, because of the offset drive shaft arrangement for the typical two-stroke chain saw engine, an adaptor must be provided to transmit power to the flexible drive shaft through a ninety degree gear box. This results in increased weight and cost because of the requirement for chain, sprockets and gear box. These attachments have not been well accepted.
Another difficulty encountered in adapting a conventional chain saw two-stroke engine for powering a portable tool such as a line trimmer is that the chain saw engine is designed primarily for relatively high speed, low torque cutting operations, while applications such as line trimmers require relatively high torque, low speed operation. Therefore, the typical chain saw two-stroke internal combustion engine is not ideally suited for such applications, and such use tends to result in shortened engine life.
A problem incidental to adapting a chain saw engine for line trimmer applications and the like is the location of the muffler mounted on one side of the engine housing which limits the option of the operator for using the assembly in either right or left handed operation. This side mounted muffler configuration also results in a potentially dangerous situation when the unit is rotated ninety degrees so that it can be used for lawn edging.
Finally, when the engine is disposed behind the operator when in use, the center of gravity of the assembly is typically behind and above the operator's hands, thereby making the assembly very awkward to maneuver.